Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$114.83	3.368%	$118.6975	$118.70	$118.70	$118.70
Purchase #2	$156.56	5.332%	$164.9078	$164.91	$164.90	$164.90
Purchase #3	$140.54	7.161%	$150.6041	$150.60	$150.60	$150.60
Purchase #4	$35.60	10.153%	$39.2145	$39.21	$39.20	$39.20
Purchase #5	$123.90	13.820%	$141.023	$141.02	$141.00	$141.00
Purchase #6	$24.43	3.447%	$25.2721	$25.27	$25.25	$25.30
Purchase #7	$63.41	11.362%	$70.6146	$70.61	$70.60	$70.60
7 purchase totals =	$659.27		$710.3336	$710.32	$710.25	$710.30